Increasingly, researchers are demystifying the many ways that our microbiome affects our broader health. “Gut health is really important,” registered dietitian Kristin Kirkpatrick, RD, tells the Cleveland Clinic. “There is so much attention and research on the microbiome and gut health now that experts often refer to it as the ‘second brain,'” she says.
Now, new research suggests that eating too much of one food in particular—a prebiotic “found in a lot of foods that you probably already eat”—can cause outsized liver cancer risk in some, despite having a broader reputation as a harbinger of health. Read on to learn which food item could spike your liver cancer risk by 40 percent, and why only some people experience this problem.
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Your gut microbiome is made of trillions of micro-organisms that live in your stomach and intestines. “In a healthy person, these ‘bugs’ coexist peacefully, with the largest numbers found in the small and large intestines but also throughout the body,” explains the Harvard T.H. Chan School of Public Health, noting that these facilitate the day-to-day functioning of the human body. “The microbiome consists of microbes that are both helpful and potentially harmful. Most are symbiotic (where both the human body and microbiota benefit) and some, in smaller numbers, are pathogenic (promoting disease),” they note.
Now, some researchers say that one particular prebiotic affects liver cancer risk by altering your gut health—and argue that this fits into their broader understanding of how gut health impacts overall health. “We have worked for a long time on this idea that all diseases start from the gut,” said Matam Vijay-Kumar, PhD, a study author and professor in the Department of Physiology and Pharmacology in the College of Medicine and Life Sciences and the paper’s senior author.
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According to the new study, which was performed on lab mice, individuals who eat diets rich in refined fiber such as inulin may be at increased risk of liver cancer. The researchers observed that one in 10 of the healthy animals developed liver cancer after consuming an inulin-containing diet.
“That was very surprising, given how rarely liver cancer is observed in mice,” Vijay-Kumar told Science Direct. He says that though fiber is a healthy addition to most people’s diets, “the findings raised real questions about the potential risks of certain refined fibers.” Inulin-containing foods include whole wheat, and certain fruits and vegetables, including asparagus, bananas, and garlic.
Over the course of their study, the researchers realized that the mice who went on to develop liver cancer all had one thing in common: they had an excess of bile acids in their blood caused by a previously unnoticed congenital defect, known as a portosystemic shunt. In fact, 100 percent of mice with this abnormality went on to develop malignancy, while none of the mice with low bile acids had this problem while being fed the same diet.
The researchers believe this occurred because of an inflammatory response which can be generated as blood leaves the intestines. Under usual circumstances, that blood goes into the liver, where it is filtered before returning to the rest of the body. However, when the mouse had a portosystemic shunt, the blood from the gut would sidestep the liver and end up back in the body’s general blood supply while still containing a high concentration of microbial products. These stimulate an inflammatory immune response, which can ultimately lead to cancer.
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The key takeaway, according to the researchers, is that from one individual to the next, our bodies handle nutrients differently. According to additional data they collected from human serum samples, men who had the highest blood bile acid levels and consumed a high fiber intake had a 40 percent increased risk of liver cancer. However, men with the lowest blood bile acid levels who had a high overall fiber intake saw a 29 percent lower risk of liver cancer.
The study authors say these findings support the need for more blood bile acid level testing. Those who are aware they have abnormally high levels of bile acids should consider altering their diets with the help of a doctor or nutritionist. “All fibers are not made equal, and all fibers are not universally beneficial for everyone. People with liver problems associated with increased bile acids should be cautious about refined, fermentable fiber,” Beng San Yeoh, a postdoctoral fellow and the new paper’s first author, told Science Direct. “If you have a leaky gut liver, you need to be careful of what you eat, because what you eat will be handled in a different way.”